title: High-temperature mass spectrometric determinations of relative ionization cross-sections of gaseous TiO, TiO2, VO, VO2, YO, HfO and GeO molecules.
abstract: BACKGROUND
  Accurate values of electron ionization cross-sections of high-temperature vapor species are of importance in mass spectrometric investigations as well as in a variety of other fields. However, the present experimental techniques are subject to many inherent difficulties or are limited in applicability and so far have yielded relatively few reliable values. Theoretical calculations are not sufficiently accurate. So the need for experimental ionization cross-section data for these species is very important.
  
  
  METHODS
  Measurements were performed by high-temperature Knudsen effusion mass spectrometry with a MS-1301 mass spectrometer. Vaporization was carried out using molybdenum effusion cells containing samples of pure Au, V2O3, Ti3O5, GeO2 and Y2O3-HfO2 systems.
  
  
  RESULTS
  The VO, VO2, TiO, TiO2, YO, HfO and GeO vapor species were identified over the samples studied. The partial pressures of Au and the oxides were measured by a complete isothermal vaporization method. The relative ionization cross-sections σ(Au)/σ(i) were determined for the gaseous oxides studied. The results were compared with the literature data.
  
  
  CONCLUSIONS
  The inapplicability of the 'additivity rule' is shown. This finding is in good agreement with a tendency to changing ionization cross-sections in the Periodic Table row of gaseous M, МО and МО2 species.
authors.affiliation: Chemical Department, St. Petersburg State University, Universitetskii pr. 26, 198504, Saint Petersburg, Russia.
authors.forename: Sergey I
authors.initials: SI
authors.lastname: Lopatin
authors.forename: Sergey M
authors.initials: SM
authors.lastname: Shugurov
authors.forename: Ksenia A
authors.initials: KA
authors.lastname: Emelyanova